TOOLS OF STONE WARE. 257 



curding to tl\e estimate of sulphate of barytes, which I have 

 used, we shall find it to be 



Sulphuric acid 33-05 



Alumine 12*53 



Potash 7-90 



Welter 46-52 



100. 

 Whithy, lOth March, 18 10. 



II. V -.r.,.] ■■>:■:■- 



Tools to ansicer the Purpose of Files and ether TnstrumentSf 

 for various Usea, made of Slone-ivare. By G. CuMUEtt- 



.;... , . irf {m'i To Mr. NICHOLSON*: u?l-if^- ' 

 SIR, .;*jqB9if',> 



Jl O some men, but not to you, will it appear a trifle, be- ciay-eninlored 

 cuuse very obvious on reflection, to have applied so soft a 'o abra4e hard 

 substance as clay to the purpose of lograting the Hardest bo- 

 dies; neitlier should I perhaps have ever thought of such an 

 application in the form I now use it, had 1 not found, in 

 bhaping some substances, that the wear of my Steel tiles was 

 rather expensive. 



It then tirst occurred to me, in ranging in thought after a Tools made cf 

 remedy, that, as our stone-ware is so hard as to blunt our it for ihi» par- 

 ■ files, tiles might be as well made of our stone ware. This wus ''°*^' 

 ' about two years ago, and the first use I made of the sugges- 

 tion was, to fold up in muslin, cambrick, and Irish linen, se- 

 parate pieces of wet clay, forcing them by the pressure of 

 the hand into the interstices of the threads, so as on divest- 

 ing them of the covering to receive a correct mould. These I 

 had well baked, and immediately found I had procured an 

 .intire new species of file, capable ev«n of de&trqying steel; 

 j,aud very useful indeed in cutting glasg> poJi&bing, a^fl ga^- 

 .i ng wood, ivory, and all sorts of metals. ,; , ;: 



The .ease with which I had accomplished my purpose, as Uses to which 

 is too often the case, made me conteut myself .with th<; yse ^'^^^^rj'^^ **" 

 L, YoL.XXV.— April, 1810. S of*^'^' 



